Adaptive photoscreening system

ABSTRACT

Briefly described, one embodiment of the system, among others, can be implemented as follows. The system includes a computer control system and an environmental light source that is controlled by the computer control system such that an amount of light provided by the environmental light source is adjusted by the computer control so that ocular parameters of an examinee are within a targeted range. Further, the system includes an irradiation system that provides multiple angle and axial eccentricity illuminations and selective wavelength irradiation based upon instructions received from the computer control system, wherein the computer control system instructs the irradiation system to provide different irradiation characteristics for different screening procedures. Also, the system includes an image detection system that captures ocular images of the examinee, wherein the computer control system analyzes captured images and provides results of in-situ analysis. The system can further include a device, for example a lens or lens system, positioned in the system to be between the eye of the examinee and the image detection system during photoscreening for shifting the neutralization of the system to a desired region for a specific population of examinees. Other systems and methods are also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of co-pending U.S. utilityapplication entitled, “Adaptive Photoscreening System,” having Ser. No.12/234,947, filed Sep. 22, 2008now U.S. Pat. No. 7,878,652B2 , which isa continuation in part of U.S. utility application entitled “AdaptivePhotoscreening System” having Ser. No. 11/338,083, filed Jan. 24, 2006,now U.S. Pat. No. 7,427,135, which are incorporated by reference intheir entirety as if fully set forth therein.

TECHNICAL FIELD

The present disclosure is generally related to medical screenings and,more particularly, is related to ocular screening and analysistechniques.

BACKGROUND

Vision disorders affect over 150 million Americans and are the mostprevalent handicapping conditions in childhood. Early detection ofvision disorder increases the likelihood of effective treatment that candecrease the negative impact of vision disorders and can improve thequality of life.

Vision screening is particularly important at early age. The AmericanAcademy of Pediatrics (AAP), American Academy of Ophthalmology (AAO),American Association for Pediatric Ophthalmology and Strabismus (AAPOS),and American Optometric Association (AOA) recommend that visionscreening should be performed at the earliest possible age and atregular intervals during childhood. However, more than 85% of preschoolchildren have never received comprehensive eye examinations, and morethan 78% of preschool children have never received any type of visionscreening. Further, a 1999 report of American Foundation for VisualAwareness indicates that school vision screening identifies only one outof four children who have vision problems.

Some vision problems, if undetected and untreated, can prevent properdevelopment of the brain's binocular function, such as a condition ofamblyopia or lazy eye. Because children's eyesight and ocular functionsare not fully developed until age 5-6, the damage can be permanentunless the “neglected” eye is corrected before the critical age of 5-6.The most common causes of amblyopia (2-5% in the US) are anisometropia(the refractive error difference between two eyes) and strabismus(crossed eyes, 3-4% in the U.S.). However, no current device that isappropriate for large-scale screening simultaneously satisfiesmulti-functional assessment requirements of AAP guidelines with thedesired performance of efficiency and accuracy, or sensitivity andspecificity.

Thus, a heretofore unaddressed need exists in the industry to addressthe aforementioned deficiencies and inadequacies.

SUMMARY

Embodiments of the present disclosure provide systems and methods forperforming customized photoscreening. Briefly described, one embodimentof the system, among others, can be implemented as follows. The systemincludes a computer control system and an environmental light sourcethat is controlled by the computer control system such that an amount oflight provided by the environmental light source is adjusted by thecomputer control so that ocular parameters of an examinee are within atargeted range. Further, the system includes an irradiation system thatprovides multiple angle and eccentricity illuminations and selectivewavelength irradiation based upon instructions received from thecomputer control system, wherein the computer control system instructsthe irradiation system to provide different irradiation characteristicsfor different screening procedures. Also, the system includes an imagedetection system that captures ocular images of the examinee, whereinthe computer control system analyzes captured images and providesresults of in-situ analysis. In an additional embodiment, the computercontrol system displays a video feature to the examinee, where ocularmovement and accommodation of the examinee is controlled by use of thevideo feature.

In one embodiment, a system for photoscreening an eye of an examinee isprovided, the system including: an image display; an ocular irradiationsource; an image detection system that captures one or more ocularimages of the examinee when viewing the image display when the ocularirradiation source is active; and a device, for example a lens or lenssystem, positioned in the system to be between the eye of the examineeand the image detection system during photoscreening for shifting theneutralization of the system to a desired region for specific populationor age group of examinees. The ocular irradiation source can include asource for infrared ocular irradiation or a source for visibleirradiation or both. The source for infrared irradiation can be, forexample, a source fore coaxial and/or eccentric infrared irradiation.The image display can be either a two-dimensional or a three-dimensionaldisplay or both and can act as environmental lighting to control ocularconditions.

Embodiments of the present disclosure can also be viewed as providingmethods for performing ocular photoscreening. In this regard, oneembodiment of such a method, among others, can be broadly summarized bythe following steps: performing an automated screening procedure;analyzing the ocular images to assess at least one ocular condition; andproviding results from the analyzing step, where the screening procedureincludes the steps of: adjusting environmental lighting so that ocularparameters of an examinee are within a targeted range; displaying avideo feature to direct focus of an examinee in a desired location; andacquiring ocular images of the examinee.

In one embodiment, a method of performing photoscreening of an eye of anexaminee can be provided, comprising the steps of: displaying an image;activating an ocular irradiation source; capturing one or more ocularimages of the examinee with an image detection device when viewing thedisplayed image when the ocular irradiation source is active;positioning a device, for example a lens or lens system, between the eyeof an examinee and the image detection device during photoscreening forshifting the neutralization of the system to a desired region for aspecific population of examinees; analyzing the one or more ocularimages to assess at least one ocular condition; and providing theresults from the analyzing step. The positioning of the device betweenthe eye of an examinee and the image detection device can be either in afixed position or an adjustable position, and the position of the deviceor a part of the optical elements of the device can be adjusted duringthe analysis step. The ocular irradiation source can include a sourcefor infrared ocular irradiation or a source for visible irradiation orboth. The source for infrared irradiation can be, for example, a sourcefore coaxial and/or eccentric infrared irradiation. The image displaycan be either a two-dimensional or a three-dimensional display or bothand can act as environmental lighting to control ocular conditions.

Other systems, methods, features, and advantages of the presentdisclosure will be or become apparent to one with skill in the art uponexamination of the following drawings and detailed description. It isintended that all such additional systems, methods, features, andadvantages be included within this description and be within the scopeof the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present disclosure can be better understood withreference to the following drawings. The components in the drawings arenot necessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present disclosure. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a block diagram representing one embodiment of an AdaptivePhotoscreening System (APS) of the present disclosure.

FIG. 2 is diagram of a perspective view of a layout of the APS system ofFIG. 1.

FIG. 3 is a diagram of a setup that may be used for either the infraredor visible camera systems of FIG. 1, for one embodiment.

FIG. 4 is a table showing adaptive illumination controls for a varietyof test functions of one embodiment of the APS system of FIG. 1.

FIG. 5 is a table displaying age- and gender-specific procedures thatare performed in one embodiment of the APS system of FIG. 1.

FIG. 6A is a diagram of a setup of an infrared image detection systemand irradiation source for a refraction test for one embodiment of theAPS system of FIG. 1.

FIG. 6B is a diagram of a bell shape normalized integrated intensityprofile used to determine a refractive error by an embodiment of the APSsystem of FIG. 1.

FIG. 6C is a diagram of an irradiance arrangement utilized in anembodiment of the APS system of FIG. 1.

FIGS. 6D-6E are diagrams of three-dimensional bell-shape intensityprofiles obtained using the irradiance arrangement of FIG. 6C by anembodiment of the APS system of FIG. 1.

FIGS. 6F and 6G are diagrams of a setup that may be used for either theinfrared or visible camera systems of FIG. 2, for another embodiment.

FIG. 6H is a diagram of a plot of APS refraction measurement of an eyemodel based on a neutralization region around −1 diopter.

FIG. 6I is a diagram showing the effect of the inclusion of a lens forshifting the neutralization region illustrated in FIG. 6H.

FIG. 6J is a plot comparable to that of FIG. 6H showing, however, a +2diopter shift of the neutralization region.

FIG. 6K is a plot showing the effect on the change in distance at whicha virtual image is seen by the eye as affected by the distance of thelens of FIG. 6I from the eye.

FIG. 6L is a plot showing the change in image magnification as a resultof change in the position of the lens of FIG. 6I in respect to the eye.

FIG. 7A is a diagram of an irradiation source and camera for a dynamicfixation and alignment test from the viewpoint of an examinee, in oneembodiment of the APS system of FIG. 1.

FIG. 7B is a diagram of a plot of a gazing trajectory for a subject'seye being measured by an embodiment of the APS system of FIG. 1.

FIGS. 7C-7E are diagrams of various schemes to Cover-Uncover a subject'seyes during an eye examination using an embodiment of the APS system ofFIG. 1.

FIG. 8 is a diagram of an arrangement of an irradiation source andcamera for corneal irregularity and optical opacity test from theviewpoint of the examinee, in one embodiment of the APS system of FIG.1.

FIG. 9 is a flow chart describing one embodiment of an auto-analysisprocedure for one embodiment of the APS system of the FIG. 1.

FIG. 10 is a flow chart describing one embodiment of a method performedby the target finding module of the APS system of FIG. 1.

FIG. 11 is a flow chart of one embodiment of a method implemented by animage quality assessment module of one embodiment of the APS system ofFIG. 1.

FIGS. 12-13 are diagrams of a two-outcome frequency distributionfunction for a measured parameter by one embodiment of the APS system ofFIG. 1.

FIG. 14 is a flow chart describing one embodiment of a methodimplemented by the APS system of FIG. 1.

FIG. 15 is a block diagram representing logic components for oneembodiment of the APS system of FIG. 1.

FIG. 16 is a flow chart describing one embodiment of a screeningprocedure utilizing one embodiment of the APS system of FIG. 1.

DETAILED DESCRIPTION

Early detection of abnormal conditions or vision problems is desirableand is very important, because such conditions are threatening to life,sight, and/or development. This need exists in the U.S. and even more soin developing nations and other nations where medical resources areseverely limited. Accordingly, one embodiment, among others, of thepresent disclosure provides in situ, real-time computer analysis ofocular images to determine and classify photoscreening image results asnormal or abnormal in each of five screening areas. Further, inaccordance with the present disclosure, non-medical personnel mayperform screening tests using a comparatively inexpensive ocularscreening device, which is characterized by transportability androbustness.

FIG. 1 shows one embodiment of an Adaptive Photoscreening System (APS)100 of the present disclosure. APS 100 applies advanced photoscreeningtechnology along with eye tracking, dynamic visual stimulus, andcomputer-assisted image interpretation to enhance the accuracy of visionscreening as requirement described by AAP guidelines. The evaluationprocesses of embodiments of APS 100 include ocular analysis &assessments, such as those involving binocular refraction condition,ocular motility & alignment, optical opacities, cornea irregularity,retinal tumors, and color-blindness. Therefore, one embodiment of theAPS system 100 is an integrated ocular screening system thatincorporates advanced imaging that may assist physicians, nurses,educational institutions, public health departments, and otherprofessionals who perform vision evaluation services. As such,embodiments of the APS system 100 remedy many known deficiencies ofcurrent screening devices.

Elements of the APS system 100, in one embodiment, includecomputer-controlled visible ocular-irradiation source(s) 141,near-infrared (NIR) ocular-irradiation source(s) 142, environmentalradiation source 120, visual stimulus video screen 130, visible andinfrared digital image detector 150, and computer control 110 forperforming registration, monitoring, calibration, testing control,quality control, and auto-analysis algorithms, among other functions.Note, in some embodiments the visible and infrared image detector 150constitutes individual infrared and visible cameras. While in someembodiments, a single camera may be used to obtain infrared and visibleimages.

As such, the APS system 100 provides temporal and spatial resolutionsthat are used to provide ample sensitivity and specificity for detectionof ocular function and abnormalities; quantitative assessment of resultsneeded for making medical referral determinations; and provisions forboth local data archival and also electronically transmitted remote dataarchival.

In one embodiment, the near-infrared ocular irradiation source 142includes a two-dimensional infrared display (e.g., infrared LEDassembly), and the visible ocular irradiation source 141 includes avisible light source display, which may be constructed with visible LEDsin selected wavelengths. A digital image detector 150 includes amulti-frame digital camera that is capable in detecting both visible(RGB) and infrared signals, an optical beam splitter, and a mirror. Inone embodiment, the near-infrared ocular irradiation source 142, thevisible ocular irradiation source 141, and the digital image detectors150 are assembled and fixed at a lower section of the video screen 130,which may be a LCD flat screen, as shown in FIG. 2. This portion of theAPS 100 is lightweight and is easy to position directly in front of anexaminee.

Also shown in FIG. 2, in one embodiment, an adjustable mirror 133 may bepositioned between the integrated camera/irradiation source unit 210 andthe video feature display 130, to align the stimulus field-of-view ofthe examined eye and the detection field of the camera. For an infraredapplication, mirror 133 may be a hot mirror that reflects near 100% ofinfrared. For visible application, mirror 133 may be a mirror or opticalbeam splitter. When beam splitter is used, the portion of video displaybehind the beam splitter acts as the visible irradiation source.

The environmental illumination source 120 may be the illuminationproduced by the programmed video 130 itself or, when the illumination isnot sufficient in control of pupil response, some visible LEDs positedby the sides of the video display 130.

FIG. 3 shows a possible arrangement of the integrated camera/irradiationsource unit 210. The coaxial irradiation is produced by the use of apellicle beam splitter 305. The coaxial light source may be one of theLEDs on the right panel that is projected onto the center of theentrance pupil 320 of the detector 150. If the size of LED is smallcompared to the camera pupil size, multiple irradiation sources (LEDs)become near-coaxial. Eccentric irradiation is provided by the LEDsarranged on both the right and bottom panels as shown in the figure.

The computer control 110 (e.g., a laptop PC) controls APS 100, includingremote optical and light elements (e.g., image detectors 150, LEDdisplays 141, 142, environmental illumination 120, video display 130,etc.). In one embodiment, the computer control 110 is configured todisplay a user-interface program that enables a trained operator tolaunch a video feature for the examinee. In one embodiment, the videofeature being displayed on the video screen 130 attracts the attention(e.g., controls accommodation status and ocular fixation) of examineesthroughout examination procedures. For a young examinee, an animationcharacter of his/her choice may be used in the screening procedure. Viathe video camera 150 and a small continuous irradiation, an operatorensures that the examinee is properly positioned within thefield-of-view of one camera. Infrared irradiation can provide strongretinal reflex for the detector that is invisible to examinee. While theexaminee is watching the animation, the examinee's cornea reflections,which determine his/her ocular gazing angle and convergence, arecalculated with the computer control system 110 in real time. Theanimation feature may be used to control an examinee's ocular motion aswell as emotion. For example, an on-screen character within theanimation feature may be programmed to “walk off the screen” if theexaminee is not in the proper viewing range. Therefore, ocular movementand accommodation can be well controlled by the APS 100 in performingocular measurements.

The incident light that is projected onto an examinee's retina isdiffusively scattered and passes back through all the ocular elements onthe return path. The information the light carries (that is captured inthe photoscreening image) is in some ways similar to that provided by awave front aberration method that describes individual ocular opticalperformance. However, the information content of the photoscreeningimage includes measures of at least one or more of five ocularcharacteristics that are potentially useful for vision screening, suchas:

-   -   A. Refractive status of eyes that can be obtained by        photorefraction theory under proper control of chromatic and        monochromatic aberrations as well as the ocular gazing angle;    -   B. Ocular orientation and convergence that can be obtained        through binocular Purkinje reflections using the Hirschberg        method;    -   C. Optical opacities that can be observed through the uniformity        and both spectral and spatial radiance distributions of the        red-reflex;    -   D. Retinal tumor that can produce an abnormal spectral, or        color, distribution in the retinal reflex; and    -   E. Irregular cornea surface that distorts the shape and the        reflected irradiance distribution of the incident light beam        similar to the red-reflex observation through the retinoscope        and ophthalmoscope.

In doing so, the APS 100 provides environmental illumination controlthat adapts to an individual's pupillary response to light and radiationsource (141, 142) intensity that adjusts to individual retinalreflectance. FIG. 4 is a table showing adaptive illumination controlsfor a variety of test functions.

As shown for a refractive test (310), the environmental lighting for theroom is bright and adapted in response to examinee's pupil response tothe light. A pulsed NIR irradiation source is used, where radiationintensity is adapted in response to the examinee's retinal reflectance.For a fixation and ocular alignment test (320), continuous blue light isprovided by the radiation sources and bright, blue-free, light isprovided by the environmental light source. For combined optical opacityand cornea examinations (330), pulsed near-infrared radiation isprovided by the irradiation sources and the environmental light sourceis not used so that the room is maintained dark and the examinee'spupils are naturally dilated. For a retina spectrum test (340), pulsedwhite light (having broad band spectrum that is sensitive to all R, G,and B camera detections) is provided by the radiation sources and theenvironmental lighting is kept dark for the same reason in 330. For acolor blindness test (350), no radiation source is provided and it isarbitrary as to the environmental lighting.

Next, examination procedures are described for one embodiment of the APS100. First, an operator enters patient data that is provided by anexaminee, parent of an examinee, or other adult, while the examineewatches an entry video or animation feature at a preset distance ofabout two-three of a meter from the examinee. The operator initiates thescreening procedure by either touch-screen contact or by programmed LCD(liquid crystal display) sequence based on input patient characteristicsor demographics, including age and gender. After which, a variety oftests may then be performed. FIG. 5 displays age- and gender-specificprocedures that are performed in one embodiment. These procedures arediscussed in greater detail hereinafter.

Via the APS system 100, a data acquisition process is executed. The APSsystem 100 acknowledges the acquired data in selecting screeningprocedures that are applicable for the age, gender, and race of theexaminee. Further, measurements obtained by the APS system 100 may becalibrated with respect to individual factors obtained from the initialdata acquisition process. For example, the variation of the spectralreflectance of individuals can have significant effects on the eccentricmeasurements. This effect, however, may be eliminated or mitigated bynormalizing such data for each eye with the total signal of thecorresponding coaxial photoscreening image, as performed in one or morephotoscreening procedures of the present disclosure.

Photoscreening Procedures and Tests

A. Binocular Refractive Test

One automated ocular screening procedure performed by an embodiment ofthe APS system 100 is a binocular refractive test (which corresponds toitem 310 in the table of FIG. 4). A binocular refractive test isrecommended for persons ages 3½ years and up. For younger children, thelogic of the APS system 100 is configured to bypass this test andperform other applicable test(s) for the examinee's age range andgender.

To start the procedure, an examinee is positioned in front of the videoscreen 130 and is monitored by the infrared video camera 150. Thecoaxial infrared irradiation (142) is used to illuminate the subject.The infrared images of pupils are captured and the pupil diameters aredetermined in real time with the computer program. The room orenvironmental lighting 120 and the video irradiance 130 are red-free toprevent interference of the infrared detection. The illumination fromboth 120 and 130 are automatically adjusted by the APS system 100 toensure that the pupil sizes of the examinee are in the proper range of2.5-4.5 mm. Further, in one or more embodiments, the APS system 100 isconfigured to play the video (animation) with near constant irradiancebefore and through the data acquisition. An imagedetector/irradiation-source unit 210 locates right below a LCD screen130 and an animation feature being shown on the LCD screen 130 toprevent an eye lash from blocking the reflex signal detected from an eyeof the examinee.

A pellicle film beam splitter 305 (as shown in FIG. 3) is used toproject the light source space onto a respective camera entrance pupilplane 320 of camera 150 (to provide maximum freedom of light patternarrangement including all eccentric and coaxial acquisition). Thisunique technique eliminates the spatial limitation inherent inconventional photoscreening devices. From the viewpoint of the examinee,a respective irradiation source and camera are arranged as shown in FIG.6A. Also, in some embodiments, small LEDs are used so that corneareflections are minimized. Fiber optics may be use to provide improvedspatial control and beam orientation. Trial lenses (e.g., +1.5 diopter)that compensate the animation display distance (e.g. ⅔ meter) may alsobe used in front of the subject to relax accommodation for cooperativeexaminees similar to retinoscopy.

Further, the irradiance of a continuous or pulsed coaxial LED controlledby logic of the APS system 100 may be modulated until the pupilirradiance detected by the infrared camera is just below the detectionsaturation level. The radiation level of the coaxial LED is then appliedto all infrared LEDs before image data acquisition starts.

Example photoscreening images of horizontal illumination from anexaminee having a +5 diopter measurement are shown in the lower part ofthe FIG. 6A. The crescent appearances of pupillary images depend notonly on the refraction of the eye, but also the pupil size, the gazingangle, and the monochromatic aberration of the eye. The retinal reflexsignal from the infrared photoscreening image is used to calibrateretinal properties of an individual. The video digital camera 150monitors the pupil size to control the aberration and proper subjectposition and gaze angle of the examinee. The infrared images areacquired and displayed on-screen of the control computer for an operatorto see.

Exemplary, the binocular refractive test is initiated by displayinganimation characters on a video screen 130, which is used to induceproper positioning of the examinee (e.g., an energetic child). Forexample, the video screen 130 may display animation feature at a ⅔ meterdistance from subject (to provide fixed fixation target at ⅔ m). Ocularimages are then taken at 30-60 Hz (for a duration of less than a second)with the sequential programmed activation of irradiation source 142,where a narrow-band wavelength at near infrared is used (instead ofwhite light). This provides multi-eccentric plus coaxial photorefractivedata. In particular, an arrangement of a minimum of seven to the maximumof thirty-five LEDs is used in one embodiment as the irradiation source142.

As the examinee is positioned in front of the video screen 130, logic ofthe APS system 100 is configured to automatically find two infraredpupil reflections within acquired photoscreening image(s) featuring botheyes and determines the diameters of pupil reflections. If the pupildiameters are larger than 4.5 mm (or smaller than 2.5 mm), the APSsystem 100 sends a signal to increase (or decrease) the roomillumination 120 until the pupil is within 2.5-4.5 mm or reaches itsmaximum (minimum) illumination. The APS system 100 monitors individuallythe two pupil reflex irradiances captured by the camera. From thespatially integrated intensity profiles of the sequenced images,refractive errors are determined.

Note, in contrast, that some current, conventional eccentricphotorefractive (EPR) screening devices perform this test in a darkenedenvironment to achieve large pupil diameters, which can be 7 nm or morefor children. In previous studies, it has been observed that thehigh-order aberrations for such pupil diameters have significantindividual variation that may result in large errors in the visualacuity measurement.

The APS system 100 determines the refractive errors of both eyes fromthe irradiance provided by a single line of LEDs (at the same angle).The APS system 100 further determines whether astigmatism may exist fromthe irradiance provided by three lines of LEDs (that are multi-angled),in one embodiment. For example, one embodiment of the APS system is ableto detect spherical/cylindrical refractive errors at less than 0.25diopter measurement, while the axis measurement error is less than 25degrees for astigmatism. The APS system 100 is able to detect ocularconditions related to spherical, cylindrical, and axis refractiveerrors; un-equal pupil size (anisocorea); anisometropia; significantinfrared irradiance difference from two eyes, etc. via an auto-analysisprocess, discussed hereinafter.

As described above, one embodiment of the APS system 100 determines therefractive errors of both eyes from the irradiance provided by a singleline of LEDs (at the same angle). A bell shape normalized integratedintensity profile 610 (as shown in FIG. 6B) may be obtained by APS 100and used to determine the refractive error along the meridian ofeccentric illumination. In general, it is observed that the intensitybell curve becomes wider with increased pupil diameter and/or refractiveerror. By calibrating the size of the pupil of the subject to a set size(such as 5 mm), the varying shape of the intensity bell curve may beattributed to a refractive error. For example, in FIG. 6B, the intensitybell curves increase in width as the associated refractive errorsincrease in dioptive powers.

The term “bell shape”, as used above, is meant to relay that the shapeof the curve is in a nominal, but known, bell shape—it is not meant toimply that that the curve is strictly speaking a Gaussian-shaped curve.

Also, one embodiment of the APS system 100 may utilize irradianceprovided by multiple lines of LEDs (at multiple angles) in twodimensions (as shown in FIG. 6C). In FIG. 6C, six lines of LEDs arearranged in a two dimensional pattern. In one embodiment, the inner ringof LEDs extends 15.2 mm from the center with the next set of ringsextending 20.3 mm from the center; 25.4 mm from the center; 30.5 mm fromthe center; and 35.6 mm from the center respectively. The coaxial LEDlocated at the center and the two LEDs located away from the rings ofLEDs are used to set the background lighting and calibrate the subject'sretinal properties (e.g., reflectance and multiple scattering).

A three-dimensional bell-shape intensity profile (as shown in FIGS.6D-6E) may then be obtained by the APS 100 and the data of theseprofiles can be used to conclude spherical (symmetric), cylindrical(asymmetric) refractive errors, and the astigmatism axis at the sametime. In the profiles 620, 630 shown in FIGS. 6D-6E, the X and Y axesrepresent eccentricity in EPR and the Z axis represents the integratedintensity. This allows for two ocular meridians to be represented in aprofile. In the diagram of FIG. 6D, a profile 620 for an eye having a −1diopter refractive error is shown. Correspondingly, a profile 630 for aneye having a −6 diopter refractive error is shown in FIG. 6E.

FIGS. 6F and 6G show another embodiment of an adaptive photoscreeningsystem (APS) 100 of the present disclosure. Elements of the APS systeminclude a two dimensional or three dimensional image display 130providing a visual zone for a patient. The image display 130 can serveas a source for visible ocular irradiation 141 as well as theenvironmental illumination 120 to stimulate ocular response as well asto control the accommodation, gazing angle, and convergence of the eyesof the examinee. The embodiment exemplified in FIGS. 6F and 6G includesan image detector 150 and the irradiation source, 140, such as thecoaxial and eccentric infrared irradiation in the left housing. Thesystem also includes housings 160 and 180 to reflect/direct theirradiation 140 to the eyes and reflect/direct the resulted ocularsignals back to the image detector 150 through the same optical path 170and 190. Housing 180 includes a mirror for deflecting the light alongpath 190 and 170. The housing 160 includes a beam splitter thattransmits and reflects light signal of selected wavelength. Trial lenses165 are placed between housings 160 and 180 for examination of thesubject's eyes. As in the embodiment illustrated in FIG. 2, the systemcan include a computer control system 110, described elsewhere herein,that allows for real time data analysis.

A conventional photoscreening system has an inherent myopicneutralization at −1/WD where WD, in meters, is the working distancebetween the examined eyes and the photoscreening device including 150and 140. For example, a 1 meter distance corresponds to a −1 diopternear-sighted eye. This is the same phenomena as the reversal in theretinoscopy. FIG. 6H illustrates use of the present APS system and aneye model (Heine Retinoscopy Trainer eye) for refractive measurementwith the working distance at 1 meter. The refractive error of the modeleye can be adjusted, for example, from −7 to +6 diopter and the pupildiameter can be varied, for example, from 3 mm to 8 mm.

In FIG. 6H, the measured width of bell curves (as described in FIGS. 6B,6D, and 6E) was plotted in the Y-axis and the refractive error of theeye model was plotted in the X-axis. The neutralization is the turningpoint of photoscreening measurement and often the least sensitivedetection region for the refractive error measurement. As the figureshows, the eye with −1 dioptor refractive error has the thinnest bellwidth and the change of width per refraction difference is the leasesignificant around this neutralization region.

In one embodiment the APS system of FIGS. 6F and 6G further includes adevice, for example, a lens 165 (see also FIG. 6I). Lens 165 may beattached to or contained within housing 160. In one embodiment lens 165may be attached to or contained within housing 160 in a fixed position,or alternatively it may be mounted in or attached to housing 160 in amanner allowing it to be moved into or out of visual alignment in thepath of the irradiation and detection light 170 between the eye and thehousing 180. The lens 165 may be positioned between the eye(s) and thebeam splitter contained within housing 160. In yet another embodiment,lens 165 may be positioned underneath the beam splitter contained withinhousing 160, placing it inbetween the beam splitter and the housing 180in the path of the infrared light 170 transmitted from housing 160 tohousing 180. In another exemplary embodiment device 165 may take theform of a lens system having two lenses, one for each eye of thepatient. In yet another exemplary embodiment, device 165 may take theform of a lens system having two fixed lenses and one moving (scanning)lens, for example a Badal lens system. The purpose of device 165 is toshift the neutralization to a desired refractive error region to either(myopic or hyperopic) side and to increase spatial resolution in thephotoscreening image.

FIG. 6I illustrates the use of the device 165 for changing the locationof neutralization and therefore, the sensitive detection regions to adesired region for specific population or age group of examinees. Asshown on the top of the figure, the detector 150 and irradiation source140 (indicated as PR for photorefraction) are located in a workingdistance of WD in front of the eye. For example, if a lens 165 withrefractive power of Pw (in diopter) is introduced at distance d in frontof the eye, the PR image will appear to be located at a distance, S2,measured from the trial lens 165 as shown in the middle diagram and thesize of the PR device will appear to increase or reduce by a factor ofM. As a result, the new working distance is changed to be (d−S2), whichcan be either a positive or a negative value. A negative workingdistance allows the neutralization to be shifted to the hyperopicregion. The thin lens equation can be used to estimate the newneutralization and the image magnification. These equations areindicated in the figure. This simple calculation can also be derivedfrom the imaging of the eye (lower figure). From the PR camera point ofview, the eye will appear to be in a new location S1 with amagnification factor M in its size. The new working distance and theimage magnification value obtained from either calculation methods areidentical.

For example, lens 165 can be a +2 diopter lens for shifting theneutralization region from near-sightedness at −1 diopter tofar-sightedness. Using the equations in FIG. 6I, Table 1 below shows thecalculation results of new neutralization and magnification variationsas the lens 165 moves between housings 160 and 180 at a distance rangeof d=5 cm to d=26 cm to the eye. As the result shows, the newneutralization is now in the hyperopia range between +0.78 to +1diopter. FIGS. 6K and 6L illustrate the same results as given in theTable. To prove the theory, FIG. 6J shows the experimental result usingthe +2 diopter lens in the APS device and the commercial eye model asdescribed earlier. The neutralization is clearly shifted to thehyperopia of +1 diopter as intended. In this embodiment, the desiredregion for the neutralization shift is between about −2 diopters andabout +3.25 diopters

TABLE 1 new new eye location Distance working neutral- appearance Cameraof New len2 eye distance ization Magni- image eye working d S₂-d Xfication M S₁ distance cm cm D ratio ratio cm WD-d-S₁ 5 101 0.99 1.111.11 5.6 100.6 6 101 0.99 1.14 1 14 6.8 100.8 7 101 0.99 1.16 1.16 8.1101.1 8 102 0.98 1.19 1.19 9.5 101.5 9 102 0.98 1.22 1.22 11.0 102.0 10103 0.98 1.25 1.25 12.5 102.5 11 103 0.97 1.28 1.28 14.1 103.1 12 1040.96 1.32 1.32 15.8 103.8 13 105 0.96 1.35 1.35 17.6 104.6 14 105 0.951.39 1.39 19.4 105.4 15 106 0.94 1.43 1.43 21.4 106.4 16 108 0.93 1.471.47 23.5 107.5 17 109 0.92 1.52 1.52 25.8 108.8 18 110 0.91 1.56 1.5628.1 110.1 19 112 0.90 1.61 1.61 30.6 111.6 20 113 0.88 1.67 1.67 33.3113.3 21 115 0.87 1.72 1.72 36.2 115.2 22 117 0.85 1.79 1.79 39.3 117.323 120 0.84 1.85 1.85 42.6 119.6 24 122 0.82 1.92 1.92 46.2 122.2 25 1250.80 2.00 2.00 50.0 125.0 26 128 0.78 2.08 2.08 54.2 128.2

When coupled with the computer control system 110, the AdaptivePhotoscreening System of the embodiment of FIGS. 6F and 6G can be usedto obtain real-time data analysis. In use, an image, eithertwo-dimensional or three-dimensional, is displayed on the image displaydevice 130 and an ocular irradiation source is activated. The ocularirradiation source 140 may include either a source for infrared ocularirradiation 142 or visible ocular irradiation 141 or both. Further, thesource for infrared ocular irradiation can be, for example, a source forcoaxial and/or eccentric infrared irradiation. The image display devicecan be controlled to provide environmental lighting to control theocular conditions for photoscreening. One or more ocular images of theexaminee can be captured with the image detection system 150, which cancapture both visible and infrared images, when the ocular irradiationsource or sources are active. A device 165, such as a lens or lenssystem, is positioned between the eye of an examinee and the imagedetection device 150 during photoscreening for shifting theneutralization of the system to a desired region for a specificpopulation or age group of examinees. The captured one or more ocularimages are then analyzed to access at least one ocular condition suchas, in particular, a refractive ocular condition. The results can thenbe provided to the examinee from the analysis of the one or more ocularimages. The device 165 or a part of the optical elements of the devicecan be positioned in either a fixed position between the eye of anexaminee and the detection device 150 or in an adjustable positionbetween the eye of an examinee and the image detection device 150.Furthermore, during analysis of the one or more ocular images, theposition of the device 165 for shifting the neutralization of thesystem, or a part of the optical elements of the device, can beadjusted.

B. Ocular Motility/Alignment

Another ocular screening procedure performed by some embodiments of theAPS system 100 is an ocular motility and alignment test (whichcorresponds to item 320 in FIG. 4). In particular, an improved dynamicHirschberg mechanism is used to test ocular motility and alignment forchildren 6 months and up under normal room light condition, in someembodiments. Generally, this automated test acquires binocular dynamicPurkinje images in order to identify strabismus and to provide an ocularalignment assessment.

In one example of the ocular alignment and motility test, an attractingtarget or figure for an examinee moves across a video screen 130 (asrepresented by the dotted white line, in FIG. 7A, as part of ananimation feature). The attracting target 510 is displayed in red andgreen wavelengths and not blue, at a distance of ⅔ meter from thesubject to provide a moving fixation target at a ⅔ meter distance. Roomlight environment 120 is regulated by the APS system 100 to reduceretinal reflex that may interfere with a Purkinje signal.

To examine ocular alignment along a predicted trajectory on a“convergence vs. gazing angle” lane, a sequence of binocular images isacquired through the dynamic Hirschberg test period. Any deviation (intime and space) from the normal path indicates a fixation or motilitycondition. For example, for a working distance of three feet, a 15 inchvideo screen 130 extends a 30 prism diopters range of test. For a closerworking distance, the testing range is larger. Note that the test isvalid even if the head of examinee is moving during the test.

The APS system 100 fires at least one blue, continuous, light source(e.g., a small, single, narrow-band LED light) throughout the test toprevent interference from a cornea reflection from the video screen 130or other obstacles. The blue LED light source is located eccentricallyfrom the optical axis of the digital camera, which is right below thevideo screen 130 to prevent an eye lash from blocking the Purkinje andiris image. The video camera 150 records binocular images from theexaminee that are synchronized with moving targets displayed on thescreen 130. The reflection of the continuous, blue LED defines a motionand moving trajectory of the gazing angle versus near constantconvergence. From the viewpoint of the examinee through the mirror 133,a respective irradiation source and camera are arranged as shown in thelower portion of FIG. 7A.

From an acquired photoscreening image, the first Purkinje images of botheyes are used to determine the gazing angle and convergence of theexaminee. Then, by plotting the result in an X-Y statistical plotfeaturing normal and strabismus cases (ET and XT) (obtained from manyphotoscreening images from many subjects (e.g., over 400)), the locationof the plot for the examinee is observed to be in either a normal orabnormal region. Thus, a determination may be made about the ocularcondition of the examinee and whether an ocular abnormality may exist.

The above approaches reference Hirschberg testing. A standard Hirschbergtest applies an acceptable Hirschberg ratio (HR) and fovea location orangle (K) to derive an ocular gazing angle from photoscreening images.HR represents the corneal reflection movement (in mm) per unit of ocularangular rotation (in Δ). The fovea angle (K) represents the anglebetween the visual axis and the pupillary axis. There is considerablepopulation distribution scatter of the HR and K observed due toinfluences from subject differences. Therefore, a subject's actual HRand K values may differ significantly from the assumed values of HR andK based on population distributions.

Accordingly, in one embodiment, inter-subject variance of HR and K istaken into account by APS 100 to accurately measure the strabismicangle. One approach, among others, for measuring the strabismic angledetermines an individual eye's Hirschberg ratio (HR) and fovea angle (K)through a simulated gazing trajectory as opposed to assuming valuesbased on population averages. To determine a strabismus condition,ocular values and functional gazing trajectories of the subject's twoeyes are compared to each other by APS 100.

For comparison, a clinical standard for testing strabismus is theCover-Uncover test (also referred to VIP protocol). The first part ofthis test is the unilateral cover test. While wearing correctiveeyewear, the subject is asked to focus on a letter of a distance eyechart. The optometrist or person administering the test then covers thesubject's right eye while watching for a movement of the left eye. Uponremoving the occluder, the optometrist waits for a few seconds to allowthe subject's eyes to return to equilibrium and then proceeds bycovering the left eye of the subject. If the eye not being covered movesto fixate the target (with both eyes open one eye is not aimed at thepoint of interest) that eye was not being used. This is referred to as astrabismus.

The alternating cover test is similar to the unilateral cover test butthe main difference is that the occluder is switched from one eye to thenext. If the eye just uncovered moves this is called a phoria. Thismeans that in the resting position both eyes are not aimed at thetarget. Consequently, the subject must use effort to keep both eyesfixated on the target. This can cause eye strain and headaches. Prismsin the subject's spectacles or visual training may be required tocorrect the disorder.

A strabismus subject's eye movement depends on the fixating eye used topursue a dynamic target trajectory. When viewing with a strabismic eye,the target tracking is achieved with a series of refixation saccades.The transition from smooth to saccadic pursuit is accompanied by adeviation of the eye movement from the target fixation path.

Accordingly, one embodiment of an approach for determining strabismusvia the APS 100 uses a binocular orientation test. This binocularorientation test is performed under conditions of normal viewing and isuncontaminated by the eye measurement. An embodiment of APS 100 allowsthe test to be performed without alerting the subject being tested.During APS testing, binocular vision of the subject is significantlydisturbed by occluding each eye of the subject during the fixationtarget's trajectory across the viewing zone. This allows the detectionof latent strabismus.

One embodiment of APS 100 evaluates the binocular strabismic deviationangle and amblyopic response across a viewing range (binocular,monocular, and covered viewing zones) and not just at the center front.APS 100 determines HR, K, and the saccade scattering upon each eye ineach of three viewing zones through binocular stimulation photographictrajectory of an individual examinee. APS 100 also evaluates theconvergence in the three viewing zones to determine strabismic andamblyopic potential and condition.

As shown in FIG. 7B, a gazing trajectory for an eye being measured canbe plotted across the three viewing zones (“Zone 1”, “Zone 2”, “Zone3”). From the plotted trajectory, the Hirschberg ratio (HR) may bedetermined for an individual eye from the slope of the trajectory (e.g.,in the monocular viewing zone when the other eye is occluded) by APS100. Further, the fovea angle (K) may be determined by the APS 100 to bethe intersection point of the trajectory at the X-axis, where the X-axisrepresents the angle of stimulus. Based on the individual measurements,an accurate gazing angle for the subject may then be determined from theHirschberg ratio (HR) and fovea angle (K) by the APS 100.

Different embodiments of APS 100 may utilize different methods ofautomatically covering-uncovering a subject's eyes without letting thesubject become aware that one of his or her eyes is covered during astrabismus examination. For example, one method, among others, involvesthe APS 100 using a frame 710 to cover-uncover the subject's eyes forthe three viewing zones (see FIG. 7C). The frame 710 provides a windowthat produces temple side boundaries through which the subject views atarget. A second method involves the APS 100 using a nasal occluder 720to cover-uncover the subject's eyes for three viewing zones (see FIG.7D), where the occluder 720 produces a nasal-side boundary about whichthe subject views a target. A third method, among others, involves theAPS 100 using binocular tubes 730 to cover-uncover the subject's eyesfor three viewing zones (see FIG. 7E). The binocular tubes 740 produce anasal-side boundary about which the subject views a target. Bymonitoring eye movement, difference may be identified from smoothpursuit eye movement as the target moves across the three viewing zones.

C. Tests for Ocular Media Clarity, Cornea Irregularity, and RetinalTumor

An additional ocular screening procedure performed by some embodimentsof the APS system 100 is a combined test for ocular media clarity,cornea irregularity, and retinal tumor screening (which corresponds toitems 330 and 340 in FIG. 4). These tests are performed for all ages byevaluating the uniformity and distribution of the illumination and thespectrum distribution of the so-called “red-reflex.”

An existing problem with conventional systems is that when therefractive error of the eye is either near emmetropic or extreme, theconventional eccentric photoscreening image appears “dark” in the pupil(the so-called dead zone). For example with a conventional device, anormal or mild refractive error may be detected and cataracts may beundetected. However, with additional coaxial and near-coaxial infraredimages being generated at the same measurement and at the same time, asdone by an embodiment of the APS system 100, cataracts (that resemblesdark dots in the infrared image) are evident, although they would likelynot be observed using any of current photoscreening devices.

Next, an additional test performed by some embodiments of the APS system100 involves a cornea analysis to target cornea abnormality,keratoconus, and scars (which corresponds to item 330 in FIG. 4). Withthis test, one embodiment of the APS system 100 utilizes the infrareddetection system and infrared LED irradiation pattern 142 of the setupused in the binocular refractive test to induce a dark environment thatis not as bright as the environment used in the binocular refractivetest. This is done, because large pupil sizes are required to cover alarger examination area of the cornea.

Further, retinal tumor measurement using a conventional eccentricphotoscreening device is generally unsatisfactory. For example, whendetecting abnormal retinal reflectance, which can indicate certainretinal tumors such as retinoblastoma, the light beam for theconventional eccentric photoscreening device reaches the retina under atightly focused state. Thus, it covers a very small area of detectionnear the optical axis of the eye and often misses the diseased area,resulting in a needlessly high false negative outcome.

For the ocular opacity and cornea irregularity screenings (330) in APS100, pulsed infrared irradiation is used and the irradiation arrangementis similar to the refraction measurement shown in FIG. 6. However, theenvironmental lighting should be dimmed so that the examinee's pupilsare naturally dilated and the coverage of screening areas is sufficient.Based on both theoretical study and clinic trial, the observation ofocular opacities relies on the coaxial and near coaxial images. For thedetection of cornea surface irregularity, on the other hand, theeccentric images provide a strong indication.

The retinal tumor screening (340) involves a broad-band irradiationsource such as white LEDs. The irradiation should be near camera axisand the measurement requires the eyes in dilated condition as the firsttwo. The lower middle part of FIG. 8 shows a possible spatialarrangement of the infrared and white irradiation sources for test items330 and 340. With 30-60 Hz frame speed, the measurements for all threescreenings are performed together within a fraction of a second. Thewhite measurement 340 is performed as a single shot following theinfrared measurement sequence. The video (animation) display should bedimmed (or shrink into the darkness) gradually just before the dataacquisition sequence. Music/audio may be continuously played as if thevideo character is coming back to keep the examinee's attention in thedark. The infrared measurement is not visible to the examinee. Theexaminee sees only a single ‘photo flash’ for the 3 measurementsincluding items 330 and 340. To cover a larger screening area on aretina tumor, the video program may guide a cooperative examinee toperform this test with more than one gazing angle.

For younger children who are difficult to cooperate, binocularmeasurements are guided by a programmed animated feature on the videoscreen 130, and the APS system 100 decreases intensity of the featuredisplay within in a darkened room lighting condition as described. Forcooperative examinees, rather than binocular, a monocular measurementmay be performed at a closer distance to improve the spatial resolutionand to improve the coverage and likelihood of detection. Any abnormalspectral reflectance or dark spots in either eye, asymmetry between thetwo pupils in size, shape, color, and brightness corresponds to aquestionable ocular condition that generates a positive result by theAPS system 100, as discussed below.

D. Color Blindness

A further test performed by some embodiments of the APS system 100 is acolor blindness test (which corresponds to item 350 in FIG. 4). Thistest is generally performed for males over three years of age. Colorblindness occurs in about 8%-12% of males of European origin and aboutone-half of 1% of females. Although there is no treatment for colorblindness, once detected, guidance can be given to assist examinee'sparents and teachers, etc. to deal with difficulties in the examinee'slearning and daily lives. In general, the APS system 100 displays colorpictures or images on video screen 130 that can be used to detect orindicate color blindness in examinees. For example, if an examinee isunable to distinguish certain colored features being displayed in apicture, then this is an indication of color blindness.

E. Extended Applications

Dynamic APS detection may also be applied to detect other types ofocular alignment problems, such as those involving schizophrenia;autism; post traumatic stress disorder; physical and emotional abuse,dyslexia, attention-deficit hyperactivity disorder (ADHD), etc. In oneembodiment, the APS 100 directs the subject to visually pursue a targettrajectory path in a similar manner as previously described. Subjectssuffering from these types of ailments should have an irregular dynamicgazing angle trajectory (e.g., convergence and saccade and smooth pursuebehavior) that is detectable by the APS 100 using infrared monitoringwithout disturbing the subject.

Auto-Analysis

From acquired photoscreening images from the screening procedures, theAPS system 100 analyzes the images to attempt to detect ocularabnormalities by performing an auto-analysis process. Exemplary, oneembodiment of the APS system 100 employs an auto-analysis process toperform real time interpretation of vision screening images on site.

As part of auto-analysis logic, the APS system 100 is configured tosearch for and report signs of abnormalities detected in acquiredimages. To detect signs of abnormalities, a variety of measurements maybe analyzed, including: ocular divergence/gazing; pupil sizes/response;retinal reflex uniformity; retinal reflex intensity level; retinalreflex spectrum ratio; photorefractive gradient distribution; 2-eyecorrelation of all of the above; etc.

By and large, each measure has its high and/or low limits (thresholdvalues) that define the region of normal and abnormal cases. Thresholdvalues may be validated and calibrated based on clinical trial results.

As a further part of this process, the APS system 100 automaticallyclassifies an image as a “positive” image indicating that thephotoscreening image is deemed to show an ocular abnormality of sometype or a “negative” image indicating that the photoscreening image isdeemed to not show an ocular abnormality. To do so, the APS system 100compares image data or information obtained from the image withstatistical information for a variety of ocular conditions, both normaland abnormal, to determine whether the image data or information evincesnormal or abnormal ocular condition(s). With an average processing timeof less than a minute per examinee, auto-analysis process results can becategorized as: a positive group that may elicit a referral (e.g.,direct referral to an ophthalmic professional); a negative group; and anuncertain group, where the photoscreening image(s) have produced uncleardata. In one embodiment, photoscreening images from the uncertain groupare referred to trained readers for additional analysis. In anotherembodiment, the examinee is advised of the uncertainty of the resultsand is advised to seek medical examination.

In one implementation of the auto-analysis process, over 90% ofphotoscreening images (normal & significant abnormal) are identified bythe process with high confidence, and less than 10% of images areclassified as being ambiguous or providing uncertain results. Thesetypes of results show a reduction of about 92% in the manpower forphotoscreening image grading and electronic transmission in ocularevaluation as compared to conventional approaches, and this is takinginto account the use of trained readers to analyze ambiguous results. Byusing alternative measures for ambiguous results, the reduction inmanpower significantly improves further.

Accordingly, in FIG. 9, a flow chart is shown describing one embodimentof an auto-analysis procedure 900. First, in block 910, data acquisitionis performed to obtain patient information and to acquire ocular imagesfor subsequent analysis. Then, in block 920, image analysis is performedon the acquired ocular images. The type of analysis performed may dependupon the patient information acquired in the data acquisition step.Then, in block 930, a quality control step is performed to verify thedata obtained in the captured images and whether the data is sufficientfor subsequent analysis. If the data is not sufficient, then equipmentsetting and positioning, including examinee positioning, are checked andadjusted, and new data is obtained, as represented by block 940.Afterwards, the data acquisition step (910) is performed again. Afterimage data has been qualified or deemed sufficient, the image data isanalyzed to detect abnormalities within the image data, as shown inblock 950. If the APS system 100 does not detect any abnormalities(e.g., a negative result), then the results are reported to theexaminee, and the examinee may be released from the examination, asshown in block 960. If the APS system 100 does detect an abnormality(e.g., a positive result), then the examinee may receive a report on theabnormality and receive a referral to a medical professional for furtherexamination and inspection, as shown in block 970. Otherwise, if the APSsystem 100 is unable to ascertain whether a positive or negative resultis indicated by the image data, then the image data may beelectronically transferred to a remote data reading center so that theimage data can be analyzed by a trained reader. In some embodiments,alternatively, an uncertain result may be reported to the examineewithout transfer of the image data, and the examinee may be advised tohave a subsequent examination with a medical professional.

Next, various auto-analysis approaches are discussed with regard todifferent ocular screening procedures performed by logic of oneembodiment of the APS system 100. For example, one implementation of anauto-analysis process analyzes photoscreening images using threedistinct modules: a target finding module, an image quality assessmentmodule, and abnormality identification module. First, the target findingmodule is discussed.

The target finding module determines both the locations and sizes of theirises, pupils, and the centers of cornea reflections for each inputphotoscreening image. Referring now to FIG. 10, a flow chart describingone embodiment 1000 of a method performed by the target finding moduleof the APS system 100 is described. The method starts at block 1010,where an operator is prompted to provide verification of thepupil-finding capabilities of the infrared/visible camera 150, which areneeded for refractive 310, ocular opacity 330, and retina tumor 340tests. Then, in block 1020, the operator is prompted to provideverification of iris and corneal target-finding capabilities of the APSsystem 100 for assessments of ocular alignment and motility.Accordingly, control of pupil size by programmed variations of room orenvironmental lighting 120 may be performed, as shown in block 1030.Visual stimuli (e.g., video animation) are used to controlaccommodation, convergence, and gazing angle of the examinee, in block1040.

Next, with operation of the image quality assessment module, an index ofthe quality of each of the six fitted targets (2 pupils, 2 iris, 2cornea reflections) is calculated. The fitting indices are normalized tothe maximum possible values that occur for a perfect fitting ofwell-focused images of properly aligned examinees. Referring now to FIG.11, a flow chart of one embodiment 1100 of a method implemented by theimage quality assessment module is described. First, in block 1110,auto-calibration of examination equipment is performed. For example, thelens of respective camera 150 is automatically adjusted to frame theregion of the eye(s) of an examinee that is of interest for a particulartest. Further, room/environmental lighting 120 is automatically adjustedto the correct setting for obtaining a desired ocular response. Inparticular, image intensity is calibrated and normalize to offseteffects from environmental illumination variation and result noiselevel; light source intensity is adjusted to counteract effects fromaging and detection gain; and individual retinal reflectance propertiesare calibrated to attempt to ensure the best image quality.

Next, in block 1120, after a photoscreening image is captured, the imageis analyzed for bad image data and technique faults (e.g., improperequipment setup) to ensure quality control. For example, within acaptured image, one or more of the following regions are attempted to bedetermined by the APS system: iris locations; cornea reflectionslocations; pupil locations; and pupil diameters. Each has its index ofgoodness-of-fitting, and the APS system 100 attempts to identifyoff-focused images and images with hair, eye lash, eye lids that blockpupils, both eyes looking away from camera, very small pupil(s), etc.

For defocused photoscreening images or for partially truncated irises orpupils (e.g., resulting from squinted eyes or eyes partially blocked byhair or hand), the fitting index ranges from zero to one in order ofincreasing quality of the image. This quality control index provideseither an alert (1130) during the analysis of an unreadable image or ameasure of the reliability of analysis result(s).

Signs of abnormalities detected by the APS system 100 are targeted toreveal ocular conditions, including the following: strabismus;anisocoria; ptosis; optical opacities; tumor; refractive errors;anisometropia; amblyogenic conditions; keratoconus; color blindness;etc. In one embodiment, the abnormality identification module includesthree elements: a strabismus module that analyzes the locations of thecorneal reflections, an eye-correlation module that compares differencesof retinal reflex between two eyes, and a single-eye module thatexamines abnormalities of each eye. The measured values and anyconsequent referral decisions are affected by the parameter distributionfunctions of each module, or filter.

To illustrate, FIG. 12 shows a two-outcome frequency distributionfunction for a measured parameter by the APS system 100. In thisexample, the frequency distribution displays positive and negativefunctions, respectively, that represent measured values corresponding topositive criteria (that may elicit a referral) and negative criteria(that signifies a healthy condition). The cases that satisfy thepositive criteria exhibit a fraction of false positive results andsimilarly for the negative cases. In such embodiments, where it is anobjective to obtain a two-parameter outcome, a “cut-parameter” isutilized to discriminate positive and negative results.

In alternative embodiments, where a three-outcome distribution (e.g.,referral or positive, non-referral or negative, and undetermined), twocut-parameters are utilized (e.g., T1 and T2). FIG. 12 shows such a casefor the single-peak distribution of both positive and negative results.Accordingly, the locations of two cut-parameters are selected to obtainsimultaneously high predictive values of the positive and negativeoutcomes and acceptable values of the undetermined outcomes.

The final grading report determined by the APS system 100 is based uponthe combined results of all three modules (strabismus, eye-correlation,and single-eye). For photoscreening images that are in a negativedistribution for all three modules, negative reports result. For imagesthat are in a positive distribution for one or more modules/filters,positive grading results. For the remainder, uncertain results aredetermined and transfer of image data to trained readers may berecommended.

A more complex distribution is shown in FIG. 13 in which it features anasymmetric bimodal positive distribution and a single mode negativedistribution. In this case, high- and low-thresholds or cut-parametersare used (e.g., T1, T2, T3, T4), as shown in FIG. 13. Examples of teststhat may produce results with such distributions are the convergencevalue of strabismus and the refractive status of an eye for which thedistribution peaks of abnormal response appear on both sides of thedistribution function of normal response.

By and large, in one embodiment, an abnormality module performs themethod 1400 represented by the flow chart of FIG. 14. In no particularorder, the abnormality module performs (1410) a search for abnormalocular alignment and movement by analyzing photoscreening images.Further, the abnormality module performs (1420) a search for aniscoriaand a search (1430) for abnormal retinal reflex in analyzingphotoscreening images. Results of the searches are then reported (1440).

Referring now to the individual sub-modules of the abnormality module,the strabismus module coordinates the center locations of the two irisesin a binocular image. The inter-ocular distance and head-tilt angle arealso calculated. Using the Hirschberg method, the related cornealreflection positions give the examinee's convergence and fixation orgazing angle, which are two variables that define the deviation of eyealignment (e.g., esotropia (ET), exotropia (XT), and normal cases) inthe analysis process. Accordingly, from these calculations, they arecompared with regions of normal, abnormal, and uncertain results toindicate whether the captured image shows an abnormality related tostrabismus, as previously discussed. In some embodiments, hypertropicconditions are also analyzed.

The eye-correlation module and single-eye module are used to examine theabnormalities in the pupil area of the image or so called retinal reflexsignal. Via the eye-correlation module, a search for anisocoria andptosis is performed by examining pupil response and eliminating datawith significant difference in pupil diameter and ocular appearance. Inparticular, each pupil image is separated into red (including infrared),green, and blue panels for all analyses by the APS system 100. Theeye-correlation module compares the difference between a left and righteye in each of the following areas: intensity; uniformity (intensitydeviation); intensity (along the eccentricity direction) gradient; andR, G, B spectrum ratios. Regions of interest are then compared againstpredetermined thresholds and regions of normal, abnormal, and uncertainresults.

Also, abnormal signs may be searched in each eye. Accordingly, a singleeye module is used to separate R (red), G (green), B (blue) images andthen separate a pupil image in a direction along camera-light alignment(eccentricity directions). Each sub-area is evaluated with respect tointensity; uniformity (intensity deviation); intensity (vertical)gradient; R, G, B spectrum ratios. Regions of interest are comparedagainst predetermined thresholds and regions of normal, abnormal, anduncertain results. For APS 100, the quantitative refraction analysis isfurther performed through the ratios of total reflex intensity betweenimages.

For illustrative purposes, FIG. 15 represents one embodiment ofcomponents of logic for the APS system 100. As shown, APS logic 1500includes the following components: data acquisition module 1510,abnormality identification module 1520, quality control or image qualityassessment module 1530, target finding module 1540, strabismus module1550, eye-correlation module 1560, and single-eye module 1570, as hasbeen previously discussed. Additionally, APS logic may includeadditionally functionality (such as computer control 110) and differentembodiments may even include different functionality subsets. Thus,embodiments of the present disclosure are not limited to therepresentation of FIG. 15.

As part of the auto-analysis process for one embodiment, a computerschematic eye-model is used that reproduces optical characteristics of ahuman eye, including refractive errors and customization. Although manysuccessful eye models are available today, these models are constructedfor the emmetropic (refractive-error free) adult condition withoutpathology. In such conventional models, average measured values areadopted for all ocular optical parameters. There is no specific gender,age, or race characteristics associated with these conventional models.Further, the conventional eye models fail to describe parametervariations in the population. Such information is particularly importantin applications related to public health.

Accordingly, one embodiment of an eye-model of the present disclosureincorporates refractive errors, the most prevalent vision defect inpopulation. Hence, the correlation between refractive errors of the eyesand ocular parameters (the ocular axial lengths, cornea curvatures, andintraocular powers in particular) are featured in the eye model. Assuch, the eye model describes refractive error with variations of corneacurvature, axial length, and intraocular power simultaneously andconsiders the distributions of these parameters' variations in theexaminee's group, such as a group of young adults in a certain agerange.

Advantageously, the Adaptive Photoscreening System (APS) 100, accordingto one embodiment of the present disclosure, employs multiple lightsources 141, 142 with programmed sequenced irradiation of the eyes inthe visible (VIS) to near-infrared (NIR) regions and both still frameand video digital camera 150 (both infrared and color) to perform:binocular measurements of the refractive errors, detection of strabismusand amblyopia, cataracts or optical opacity, ptosis, nystagamus, andspecific corneal abnormalities. Further, APS 100 increases the retinalarea of observation to enhance the likelihood of the observation ofcertain types of retinal tumors as manifested by abnormal retinalreflectance. In addition, tests performed by the APS system 100 areage-specific and multi-functional with respect to abnormality detectionand satisfies the current recommended guideline from the AmericanAcademy of Ophthalmology (AAO 2003). AAP and other organizations alsogive the similar recommendations. It is noted that for the majority oftests, objective screening is recommended.

Specifically, guidelines have been proposed stating that refractiveerror should be supplemented, for example, by assessments of strabismus,motility, and inspection for ocular optical opacity and retinoblastoma.Binocular, objective measurements, as implemented by the APS system 100,fulfill these requirements in a mass screening environment. To satisfythese requirements and the desire to perform large population screeningapplications using electronic transfer of results, embodiments of theAPS system 100 enable the testing of a range of ocular functions and tooffer the significant potential for telemedicine applications.

Embodiments of the APS system 100 offer potential for application to themedically under-served population of the U.S. and to developing nationsof the world that lack the resident medical expertise and resources, inaddition to general pediatric screening. The versatile andcost-effective design of the APS 100 allows its deployment and use bytrained but non-medical operators to achieve the desired public healthscreening of children. With simple modular modifications, APS 100provides a less mobile but more capable vision evaluation system that issuitable for pediatric clinics.

Note that the set of examinations performed by embodiments of the APSsystem 100 satisfy the Eye Examination Guidelines of the AmericanAcademy of Pediatric Ophthalmologists (AAPO) and AAP announced in 2002and 2003 and are also applicable for older age groups. Further,embodiments of the APS system 100 are characterized by transportability(so that the evaluation is transportable, e.g., can be taken tochildren); simple examination procedures (which is beneficial forpre-school children); simplicity of operation; comparative low costequipment/instrumentation; and completeness and accuracy of ocularassessments.

Advantageously, in accordance with one embodiment of the APS system, anuncertainty of less than 0.5 diopter for measurement of refraction(conventional EPR systems have a standard error of ˜+−2.0 diopters) canbe achieved and used to accurately identify opacities.

Further, with the APS system 100, light sources are wavelength dependent(e.g., range from quasi-blue to near infrared), and individual ocularaberrations are able to be isolated, based on wavelength ranges, andmeasure refractive content and opacity of the eye which may bewavelength dependent, such as cataracts, floaters, retinal tumors,keratoconus, corneal scarring, corneal ulcers, etc.

Further, embodiments of the APS system 100 utilize pulsed light sources,such as a series of LEDs, among others, where each light source ispulsed on for a certain period of time. The refractive measurement maybe then made in the infrared region because the eye does not respond toinfrared light and the pupil does not contract or expand, so arefractive measurement can be made at leisure with a pulsed sourcewithout altering condition of the eye (e.g., performing refractivemeasurements utilizing a sequent infrared radiation under a lightingenvironment that is suitable for near distance visual activities, suchas reading). When measurements are made within the visible range,pupilary responses are existent and are taken into account. Accordingly,the sequence of measurement, such as the order at whichwavelength-dependent light sources are activated, may be configured toameliorate or lessen pupilary response.

Also, as described, photoscreening techniques of one embodiment of APS100 provides radiant stimuli (e.g., irradiation sources 141, 142) anddetectors 142, 150 that span the broad spectrum from visible wavelengths(e.g., RGB) to near infrared; utilizes multiple-light-source stimuli141, 142 in a two-dimensional array to cover various source-detectorangles and eccentricities; and provides digital multiple-shot imagedetectors 150 (rather than a typical single snap-shot camera). Thisthree-fold characteristic enables APS 100 to extract accurate ocularparameters by decoupling the mixed, or ambiguous, information that isoften obtained using current devices.

In contrast to a typical photoscreening image, where only partial ocularinformation is collected by a camera depending on its aperture and itsangular location relative to a light source, one embodiment of APS 100obtains improved accuracy and enhanced information content by using atime-sequence of light sources 141, 142 of various spectral signaturesand digital camera detection at two angular locations of the returningspectral radiance.

Advantageously, one embodiment of APS 100 (1) adjusts room lightenvironment 120 to control the examinee's pupil size, (2) uses anoptical beam splitter to combine illumination and detection spaces, (3)uses an infrared photorefraction (PR) image to self-calibrate retinaldifferences, (4) uses a spatially integrated intensity profile to obtainrefractive error (thereby discarding the ambiguous crescentinterpretation), (5) uses multiple-angle illuminations andeccentricities that definitively determines astigmatism, and (6) usescentro-symmetric illumination that corrects the gazing angle effect.

One advantage of the above described embodiment(s) is that it isnon-mydriatic and, therefore, requires no pupil dilation using drugs.

Next, FIG. 16 is a flow chart describing one embodiment of a screeningprocedure utilizing the APS system 100. In a first step, input patientdata (e.g., data (date/year of birth, gender, race, reside area, IDcode, etc.) is acquired (1610). This information is used to determinewhich tests are to be performed and in the data analysis to be performedlater, the information is used to determine which ocular calibrationparameters are to be used. Accordingly, the testing procedure isspecified (1615) along with an interaction video feature or game that isused for the selected testing procedure.

The APS system 100 then implements (1620) and performs the age-specifictest sequence, where the test sequence is also gender-specific, in someembodiments. Depending on age and gender of the examinee, two to fivetests may be performed, where the data is analyzed according to age andrace, in some embodiments.

Each of these tests may include the following steps: adaptivecalibration (1621) of ocular positioning (e.g., a video feature or gamewill end if the ocular positioning is not acceptable), environmentallighting to adapt to the individual pupil response to light, andradiance of infrared light sources to be use during the measurements(adapt to the retinal reflectance of the individual). Then, dataacquisition is performed (1622) including the steps of target finding(1623) and quality control (1624). If the data acquired is not above arequired quality, the step goes back to step 1622 after checking (1625)test settings and positioning of the examinee. Otherwise, while the APSsystem 100 is analyzing (1626) data, the calibration of the next testproceeds.

From data analysis (1626), results of the testing procedures arecompared against abnormality thresholds (1627). If a positive result isdetermined (1628), the determination is logged by the APS system 100.Then, the next screening procedure or test is performed (1629).Likewise, if a negative result is determined (1630), the result islogged by the system and the next test is performed (1629).

If an uncertain result is determined (1631), step 1623 is repeated for afirst instance. However, if two uncertain results occur, then anuncertain result or condition is determined (1632) and logged by thesystem. The next test then commences (1629).

If all the results to the screening procedures have been logged as beingnegative (1633), then the examinee is released (1634) from theexamination. Accordingly, if any results are positive (1635), a referralis reported (1636). Further, any uncertain results or categories arereported (1637). In some embodiments, screening results may be providedwithin a minute after the test procedure. Also, some embodiments of theAPS 100 tailor the screening methods and analysis algorithms to fit theneeds of the individual.

Components of embodiments of the present disclosure can be implementedin hardware, software, firmware, or a combination thereof. For example,in one embodiment, the APS logic is implemented in software or firmwarethat is stored in a memory and that is executed by a suitableinstruction execution system. If implemented in hardware, as in analternative embodiment, the APS logic can be implemented with any or acombination of the following technologies, which are all well known inthe art: a discrete logic circuit(s) having logic gates for implementinglogic functions upon data signals, an application specific integratedcircuit (ASIC) having appropriate combinational logic gates, aprogrammable gate array(s) (PGA), a field programmable gate array(FPGA), etc.

When implemented in software, components of the APS system 100 can bestored on any computer readable medium for use by or in connection withany computer related system or method. In the context of this document,a computer readable medium is an electronic, magnetic, optical, or otherphysical device or means that can contain or store a computer programfor use by or in connection with a computer related system or method. Inthe context of this document, a “computer-readable medium” can be anymeans that can store, communicate, or transport the program for use byor in connection with the instruction execution system, apparatus, ordevice. The computer readable medium can be, for example but not limitedto, an electronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, device, or propagation medium.

Any process descriptions or blocks in flow charts should be understoodas representing modules, segments, or portions of code which include oneor more executable instructions for implementing specific logicalfunctions or steps in the process, and alternate implementations areincluded within the scope of the present disclosure in which functionsmay be executed out of order from that shown or discussed, includingsubstantially concurrently or in reverse order, depending on thefunctionality involved, as would be understood by those reasonablyskilled in the art of the present disclosure.

It should be emphasized that the above-described embodiments of thepresent disclosure are merely possible examples of implementations,merely set forth for a clear understanding of the principles of thedisclosure. Many variations and modifications may be made to theabove-described embodiment(s) of the disclosure without departingsubstantially from the spirit and principles of the present disclosure.All such modifications and variations are intended to be included hereinwithin the scope of this disclosure.

Therefore, having thus described the invention, at least the followingis claimed:
 1. A system for photoscreening an eye of an examinee,comprising an image display; an ocular irradiation source; an imagedetection system that captures one or more ocular images of the examineewhen viewing the image display when the ocular irradiation source isactive; and a device positioned in the system to be between the eye ofthe examinee and the image detection system during photoscreening forshifting the neutralization of the system to a desired region for aspecific population of examinees.
 2. The system of claim 1, wherein thedevice is a lens or a lens system.
 3. The system of claim 1, wherein theocular irradiation source includes a source for infrared ocularirradiation, visible irradiation, or both.
 4. The system of claim 3,wherein the ocular irradiation source provides coaxial and/or eccentricinfrared radiation.
 5. The system of claim 1, wherein the image displayincludes a two-dimensional video display, a three-dimensional videodisplay, or both.
 6. The system of claim 1, wherein the image displayprovides environmental lighting to control the ocular conditions.
 7. Thesystem of claim 1, further including a computer control system, whereinthe computer control system analyzes captured images and providesresults of in-situ analysis.
 8. The system of claim 1, wherein theirradiation system provides infrared irradiation after being instructedby computer control system and visible irradiation after beinginstructed by the computer control system.
 9. The system of claim 8,wherein the image detection system captures both visible and infraredimages.
 10. The system of claim 1, wherein the system performsrefractive measurements utilizing a sequent infrared radiation under alighting environment that is suitable for near distance visualactivities.
 11. The system of claim 1, wherein the captured image isanalyzed for bad image data and technique faults to ensure qualitycontrol.
 12. The system of claim 1, wherein the desired region isbetween about −2 diopters and about +3.25 diopters.
 13. A method ofperforming photoscreening of an eye of an examinee, comprising the stepsof: displaying an image; activating an ocular irradiation source;capturing one or more ocular images of the examinee with an imagedetection device when viewing the displayed image when the ocularirradiation source is active; positioning a device between the eye of anexaminee and the image detection device during photoscreening forshifting the neutralization of the system to a desired region for aspecific population of examinees; analyzing the one or more ocularimages to assess at least one ocular condition; and providing theresults from the analyzing step.
 14. The method of claim 13, wherein thedevice is a lens or a lens system.
 15. The method of claim 13, whereinthe ocular irradiation source includes a source for infrared ocularirradiation, visible irradiation, or both.
 16. The method of claim 15,wherein the positioning of the device is selected from a fixed positionbetween the eye of an examinee and the image detection device or anadjustable position between the eye of an examinee and the imagedetection device wherein at least a part of the optical elements of thedevice is adjustable.
 17. The method of claim 13, wherein the imagedisplay includes a two-dimensional video display, a three-dimensionalvideo display, or both.
 18. The method of claim 13, wherein the imagedisplay provides environmental lighting to control the ocularconditions.
 19. The method of claim 13, further including a computercontrol system, wherein the computer control system analyzes thecaptured images and provides results of in-situ analysis.
 20. The methodof claim 13, wherein the step of analyzing the one or more ocular imagesincludes adjusting the position of the device, or a part of the opticalelements of the device, for shifting the neutralization of the system.